Fisher has made 32 regular-season and playoff appearances (20 starts) across three MLS seasons since the Sounders selected him with the 40th overall pick of the 2015 MLS SuperDraft. He featured in four of six matches last summer for the Jamaican national team during their run to the 2017 CONCACAF Gold Cup final, and holds 14 international caps to date.

He joins Reggae Boyz teammate Darren Mattocks in D.C.; like Mattocks, Fisher has a US Green Card and thus won't count toward an allotted international roster slot.

“Oniel is a versatile defender who has proven that he can compete to be a starter in this league," said United general manager Dave Kasper in a club release. “His speed and ability to get forward in the attack, along with his sound defensive ability, provides us with a solid option at either outside back positions. We look forward to integrating Oniel into the team immediately."

Fisher's signing addresses United's need for depth at the fullback slots. Of the players on the Black-and-Red's current roster, only Nick DeLeon and Taylor Kemp are regulars in those spots. Paul Arriola and Chris Durkin could also figure into wide defensive roles, as could Chris Odoi-Atsem, who is on trial after not having his contract renewed following the 2017 season.